Index
- Introduction
- Visibility
- Natural Background Visibility
- Vegetation
- Surface Water
- AQRV Type VISIBILITY
- AQRV Type WATER
- Pollutant Exposure Concern Thresholds
- General Information
Introduction
The Boundary Waters Canoe Area Wilderness (BWCAW, 1,086,954 acres) is located on the Superior National Forest in Minnesota. The northern lakes and rivers of the BWCAW border Canada and form part of the "Voyageurs Highway" of the fur trade. A portion of the area was set aside in 1926 to preserve its primitive character. In 1939, additional area was declared roadless, and in 1964 the wilderness received its present designation. Pristine lakes formed when glacial ice melted centuries ago-more than 1,100 lakes are 10 acres or larger. Heavily forested land, rock formations, wetlands, and lakes dominate the landscape.
Air Quality Related Values
Visibility
The scenic beauty of the BWCAW is highly valued by its users. Visual experiences encountered by most users consist of shoreline views and inspiring water reflected sunsets across lakes/rivers from campsites, portages, or mid-lake vantage points (from boats or canoes). Outstanding shoreline features include lichen-covered bedrock cliffs and boulders; boulder-strewn lake inlets and outlets; waterfalls and rapids; shoreline wetlands with sphagnum, labrador tea, or leather leaf and sparsely timbered with black spruce or tamarack; the big-tree character of individual or clustered old-growth red and white pine, and the contrast established by intermingled aspen and conifer stands.
Natural Background Visibility | ||||||
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Site Specific Rayleigh scattering coefficient: | Clearest 20% Natural | Clearest 20% 2000-2004 Baseline | Haziest 20% Natural | Haziest 20% 2000-2004 Baseline | Average Annual Natural | Annual Average 2000-2004 Baseline |
Standard Visual Range (km) | 299 | 217 | 126 | 56 | 205 | 119 |
Haze Index (dv) | 3.42 | 6.43 | 11.61 | 19.59 | 6.98 | 12.19 |
Vegetation
The variety of flowers in this wilderness includes subarctic species and nearly 30 native species of wild orchids. Principal conifers are jack pine, white pine, and red pine. Also common are white and black spruce, balsam fir, northern white-cedar, and tamarack. Principal broad-leaved trees are quaking aspen and paper birch.
BWCAW is characterized by the species associated with the northern Minnesota Glacial Lake Basin. Visual diversity is highest during the fall. Ground and herbaceous understory of native berries and aquatic species like wild rice are gathered by some recreationists and are a valuable food source for many animal species. Many species of sensitive plants, including ram's-head ladyslipper and northern comandra, inhabit portions of the BWCAW. Lichen flora of the BWCAW is diverse and lichen species known to be sensitive to air pollutants are common throughout the area.
Surface Water
Approximately 1,175 lakes of 10 acres or larger comprise 260,000 acres (24 percent) of the BWCAW surface area. The unique opportunity for recreational canoe/boat travel offered by high-quality interconnected lakes and waterways in a largely undisturbed scenic forest environment was the primary force behind the wilderness designation for the BWCAW. The chemistry of the lakes is an important measure of their health. Seventy percent of the lakes are considered "dark water" due to dissolved organic carbon resulting from extensive peatland. Bedrock exposures are a common feature, shaping the beds, shores, and bottoms of BWCAW lakes and streams.
Lakes and streams are habitat for walleye, northern pike, bass, crappie, sunfish, lake, and brook trout, and several other fish species. Fishing is a popular wilderness use.
Resource Concern Thresholds
AQRV Type: VISIBILITY | ||
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Sensitive Receptor | Sensitive Receptor Indicator | Thresholds |
Natural Visibility | Light Extinction | To maintain consistency with the Minnesota Regional Haze implementation plans, the visibility threshold for concern is not exceeded if the 98th percentile change in light extinction is <5% for each year modeled, when compared to the 20% best natural background values. |
Plume Blight | Absolute Contrast | For near field sources (within 50 km of a Class I area), no additional analysis will be requested If screening analysis of a new or modified source can demonstrate that its emissions will not cause a plume with hourly estimates of DeltaE (color difference index) greater than or equal to 2.0 or the absolute value of the contrast greater than or equal to 0.05 when modeled against natural conditions. |
Plume Blight | Absolute Contrast | Higher level near-field screening and refined analysis: no further analysis will likely be requested if a new or modified source can show that impacts from a new or modified source will stay with the threshold of DeltaE <1.0 and |C| <0.02 modeled against natural conditions. |
Plume Blight | Color Difference Index | Plume blight near-field refined analysis: no further analysis will likely be requested if a new or modified source can show that impacts from a new or modified source will stay with the threshold of DeltaE <1.0 and |C| <0.02 when modeled against natural conditions. |
Plume Blight | Color Difference Index | For near field sources (within 50 km of a Class I area), no additional analysis will be requested If screening analysis of a new or modified source can demonstrate that its emissions will not cause a plume with hourly estimates of DeltaE (color difference index) greater than or equal to 2.0 or the absolute value of the contrast greater than or equal to 0.05 when modeled against natural conditions. |
AQRV Type: WATER | ||
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Sensitive Receptor | Sensitive Receptor Indicator | Thresholds |
Aquatic Organisms | Chemistry | Based on the Acid Deposition Control Act passed by Minnesota, the sulfur deposition limit that would protect the most sensitive lakes and streams from acidification was set at 11 kg/ha/yr. Higher levels would be damaging. Below 6 kg/ha/yr, no damage to aquatic organisms is expected. |
Aquatic Organisms | Chemistry | Total sulfur plus 20% of nitrogen deposition at levels exceeding 12 kg/ha-yr may cause ANC loss that would impact aquatic organisms. Levels below 9 kg/ha-yr are not expected to significantly impact aquatic organisms. |
Perennial Lakes and Streams | Chronic Acid Neutralizing Capacity | To maintain healthy biological functioning, the chronic pH of perennial lakes and streams must be >= 6.0. |
Perennial Lakes and Streams | Episodic Acid Neutralizing Capacity | To maintain healthy biological functioning in perennial lakes and streams, the episodic acid neutralizing capacity must be >= 0 ueq/l. |
Pollutant Exposure Concern Thresholds | ||
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Pollutant Exposures | Level Name | Thresholds |
S +20% N | DEPOSITION | Total sulfur plus 20% of nitrogen deposition at levels exceeding 12 kg/ha-yr may cause ANC loss that would impact aquatic organisms. Levels below 9 kg/ha-yr are not expected to significantly impact aquatic organisms. |
Sulfur | DEPOSITION | Based on the Acid Deposition Control Act passed by Minnesota, the sulfur deposition limit that would protect the most sensitive lakes and streams from acidification was set at 11 kg/ha/yr. Higher levels would be damaging. Below 6 kg/ha/yr, no damage to aquatic organisms is expected. |
Plume Blight | EXCEEDANCE | For near field sources (within 50 km of a Class I area), no additional analysis will be requested If screening analysis of a new or modified source can demonstrate that its emissions will not cause a plume with hourly estimates of DeltaE (color difference index) greater than or equal to 2.0 or the absolute value of the contrast greater than or equal to 0.05 when modeled against natural conditions. |
Plume Blight | CHANGE | Plume blight near-field refined analysis: no further analysis will likely be requested if a new or modified source can show that impacts from a new or modified source will stay with the threshold of DeltaE <1.0 and |C| <0.02 when modeled against natural conditions. |
Plume Blight | CHANGE | For near field sources (within 50 km of a Class I area), no additional analysis will be requested If screening analysis of a new or modified source can demonstrate that its emissions will not cause a plume with hourly estimates of DeltaE (color difference index) greater than or equal to 2.0 or the absolute value of the contrast greater than or equal to 0.05 when modeled against natural conditions. |
Natural Visibility | EXTINCTION | To maintain consistency with Regional Haze implementation plans, the visibility threshold for concern is not exceeded if the 98th %ile change in light extinction is <5% for each year modeled, when compared to the 20% best natural background values. |
Sulfur | CHANGE | Higher level near-field screening and refined analysis: no further analysis will likely be requested if a new or modified source can show that impacts from a new or modified source will stay with the threshold of DeltaE <1.0 and |C| <0.02 modeled against natural conditions. |
Sulfur | EXCEEDANCE | The Deposition Analysis Threshold for sulfur deposition below which estimated impacts from a source are considered negligible is 0.010 kg/ha/yr. |
General Information | |
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State(s): | Minnesota |
County(s): | St Louis, Lake, Cook |
Forest Service Administrative Unit(s): | Northern Region (Region 9) -- Superior National Forest |
Size: | 1,086,954 acres |
Elevation Range: | 1,260 - 2,301 feet |
Image(s): | https://www.wilderness.net/images/ |
Detailed wilderness information: | https://www.wilderness.net |
GIS Map/Official Boundary: | https://www.wilderness.net/NWPS/ |
updated: 10/22/13